1.\" $KAME: inet6.4,v 1.21 2001/04/05 01:00:18 itojun Exp $ 2.\" 3.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the project nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $FreeBSD$ 31.\" 32.Dd August 14, 2018 33.Dt INET6 4 34.Os 35.Sh NAME 36.Nm inet6 37.Nd Internet protocol version 6 family 38.Sh SYNOPSIS 39.In sys/types.h 40.In netinet/in.h 41.Sh DESCRIPTION 42The 43.Nm 44family is an updated version of 45.Xr inet 4 46family. 47While 48.Xr inet 4 49implements Internet Protocol version 4, 50.Nm 51implements Internet Protocol version 6. 52.Pp 53.Nm 54is a collection of protocols layered atop the 55.Em Internet Protocol version 6 56.Pq Tn IPv6 57transport layer, and utilizing the IPv6 address format. 58The 59.Nm 60family provides protocol support for the 61.Dv SOCK_STREAM , SOCK_DGRAM , 62and 63.Dv SOCK_RAW 64socket types; the 65.Dv SOCK_RAW 66interface provides access to the 67.Tn IPv6 68protocol. 69.Sh ADDRESSING 70IPv6 addresses are 16 byte quantities, stored in network standard byteorder. 71The include file 72.In netinet/in.h 73defines this address 74as a discriminated union. 75.Pp 76Sockets bound to the 77.Nm 78family utilize the following addressing structure: 79.Bd -literal -offset indent 80struct sockaddr_in6 { 81 uint8_t sin6_len; 82 sa_family_t sin6_family; 83 in_port_t sin6_port; 84 uint32_t sin6_flowinfo; 85 struct in6_addr sin6_addr; 86 uint32_t sin6_scope_id; 87}; 88.Ed 89.Pp 90Sockets may be created with the local address 91.Dq Dv :: 92(which is equal to IPv6 address 93.Dv 0:0:0:0:0:0:0:0 ) 94to affect 95.Dq wildcard 96matching on incoming messages. 97.Pp 98The IPv6 specification defines scoped addresses, 99like link-local or site-local addresses. 100A scoped address is ambiguous to the kernel, 101if it is specified without a scope identifier. 102To manipulate scoped addresses properly from the userland, 103programs must use the advanced API defined in RFC2292. 104A compact description of the advanced API is available in 105.Xr ip6 4 . 106If a scoped address is specified without an explicit scope, 107the kernel may raise an error. 108Note that scoped addresses are not for daily use at this moment, 109both from a specification and an implementation point of view. 110.Pp 111The KAME implementation supports an extended numeric IPv6 address notation 112for link-local addresses, 113like 114.Dq Li fe80::1%de0 115to specify 116.Do 117.Li fe80::1 118on 119.Li de0 120interface 121.Dc . 122This notation is supported by 123.Xr getaddrinfo 3 124and 125.Xr getnameinfo 3 . 126Some of normal userland programs, such as 127.Xr telnet 1 128or 129.Xr ftp 1 , 130are able to use this notation. 131With special programs 132like 133.Xr ping6 8 , 134you can specify the outgoing interface by an extra command line option 135to disambiguate scoped addresses. 136.Pp 137Scoped addresses are handled specially in the kernel. 138In kernel structures like routing tables or interface structures, 139a scoped address will have its interface index embedded into the address. 140Therefore, 141the address in some kernel structures is not the same as that on the wire. 142The embedded index will become visible through a 143.Dv PF_ROUTE 144socket, kernel memory accesses via 145.Xr kvm 3 146and on some other occasions. 147HOWEVER, users should never use the embedded form. 148For details please consult 149.Pa IMPLEMENTATION 150supplied with KAME kit. 151.Sh PROTOCOLS 152The 153.Nm 154family is comprised of the 155.Tn IPv6 156network protocol, Internet Control 157Message Protocol version 6 158.Pq Tn ICMPv6 , 159Transmission Control Protocol 160.Pq Tn TCP , 161and User Datagram Protocol 162.Pq Tn UDP . 163.Tn TCP 164is used to support the 165.Dv SOCK_STREAM 166abstraction while 167.Tn UDP 168is used to support the 169.Dv SOCK_DGRAM 170abstraction. 171Note that 172.Tn TCP 173and 174.Tn UDP 175are common to 176.Xr inet 4 177and 178.Nm . 179A raw interface to 180.Tn IPv6 181is available 182by creating an Internet socket of type 183.Dv SOCK_RAW . 184The 185.Tn ICMPv6 186message protocol is accessible from a raw socket. 187.Ss MIB Variables 188A number of variables are implemented in the net.inet6 branch of the 189.Xr sysctl 3 190MIB. 191In addition to the variables supported by the transport protocols 192(for which the respective manual pages may be consulted), 193the following general variables are defined: 194.Bl -tag -width IPV6CTL_MAXFRAGPACKETS 195.It Dv IPV6CTL_FORWARDING 196.Pq ip6.forwarding 197Boolean: enable/disable forwarding of 198.Tn IPv6 199packets. 200Also, identify if the node is acting as a router. 201Defaults to off. 202.It Dv IPV6CTL_SENDREDIRECTS 203.Pq ip6.redirect 204Boolean: enable/disable sending of 205.Tn ICMPv6 206redirects in response to unforwardable 207.Tn IPv6 208packets. 209This option is ignored unless the node is routing 210.Tn IPv6 211packets, 212and should normally be enabled on all systems. 213Defaults to on. 214.It Dv IPV6CTL_DEFHLIM 215.Pq ip6.hlim 216Integer: default hop limit value to use for outgoing 217.Tn IPv6 218packets. 219This value applies to all the transport protocols on top of 220.Tn IPv6 . 221There are APIs to override the value. 222.It Dv IPV6CTL_MAXFRAGS 223.Pq ip6.maxfrags 224Integer: maximum number of fragments the host will accept and simultaneously 225hold across all reassembly queues in all VNETs. 226If set to 0, fragment reassembly is disabled. 227If set to -1, this limit is not applied. 228This limit is recalculated when the number of mbuf clusters is changed. 229This is a global limit. 230.It Dv IPV6CTL_MAXFRAGPACKETS 231.Pq ip6.maxfragpackets 232Integer: maximum number of fragmented packets the node will accept and 233simultaneously hold in the reassembly queue for a particular VNET. 2340 means that the node will not accept any fragmented packets for that VNET. 235-1 means that the node will not apply this limit for that VNET. 236This limit is recalculated when the number of mbuf clusters is changed. 237This is a per-VNET limit. 238.It Dv IPV6CTL_MAXFRAGBUCKETSIZE 239.Pq ip6.maxfragbucketsize 240Integer: maximum number of reassembly queues per bucket. 241Fragmented packets are hashed to buckets. 242Each bucket has a list of reassembly queues. 243The system must compare the incoming packets to the existing reassembly queues 244in the bucket to find a matching reassembly queue. 245To preserve system resources, the system limits the number of reassembly 246queues allowed in each bucket. 247This limit is recalculated when the number of mbuf clusters is changed or 248when the value of 249.Va ip6.maxfragpackets 250changes. 251This is a per-VNET limit. 252.It Dv IPV6CTL_MAXFRAGSPERPACKET 253.Pq ip6.maxfragsperpacket 254Integer: maximum number of fragments the host will accept and hold in the 255ressembly queue for a packet. 256This is a per-VNET limit. 257.It Dv IPV6CTL_ACCEPT_RTADV 258.Pq ip6.accept_rtadv 259Boolean: the default value of a per-interface flag to 260enable/disable receiving of 261.Tn ICMPv6 262router advertisement packets, 263and autoconfiguration of address prefixes and default routers. 264The node must be a host 265(not a router) 266for the option to be meaningful. 267Defaults to off. 268.It Dv IPV6CTL_AUTO_LINKLOCAL 269.Pq ip6.auto_linklocal 270Boolean: the default value of a per-interface flag to 271enable/disable performing automatic link-local address configuration. 272Defaults to on. 273.It Dv IPV6CTL_LOG_INTERVAL 274.Pq ip6.log_interval 275Integer: default interval between 276.Tn IPv6 277packet forwarding engine log output 278(in seconds). 279.It Dv IPV6CTL_HDRNESTLIMIT 280.Pq ip6.hdrnestlimit 281Integer: default number of the maximum 282.Tn IPv6 283extension headers 284permitted on incoming 285.Tn IPv6 286packets. 287If set to 0, the node will accept as many extension headers as possible. 288.It Dv IPV6CTL_DAD_COUNT 289.Pq ip6.dad_count 290Integer: default number of 291.Tn IPv6 292DAD 293.Pq duplicated address detection 294probe packets. 295The packets will be generated when 296.Tn IPv6 297interface addresses are configured. 298.It Dv IPV6CTL_AUTO_FLOWLABEL 299.Pq ip6.auto_flowlabel 300Boolean: enable/disable automatic filling of 301.Tn IPv6 302flowlabel field, for outstanding connected transport protocol packets. 303The field might be used by intermediate routers to identify packet flows. 304Defaults to on. 305.It Dv IPV6CTL_DEFMCASTHLIM 306.Pq ip6.defmcasthlim 307Integer: default hop limit value for an 308.Tn IPv6 309multicast packet sourced by the node. 310This value applies to all the transport protocols on top of 311.Tn IPv6 . 312There are APIs to override the value as documented in 313.Xr ip6 4 . 314.It Dv IPV6CTL_GIF_HLIM 315.Pq ip6.gifhlim 316Integer: default maximum hop limit value for an 317.Tn IPv6 318packet generated by 319.Xr gif 4 320tunnel interface. 321.It Dv IPV6CTL_KAME_VERSION 322.Pq ip6.kame_version 323String: identifies the version of KAME 324.Tn IPv6 325stack implemented in the kernel. 326.It Dv IPV6CTL_USE_DEPRECATED 327.Pq ip6.use_deprecated 328Boolean: enable/disable use of deprecated address, 329specified in RFC2462 5.5.4. 330Defaults to on. 331.It Dv IPV6CTL_RR_PRUNE 332.Pq ip6.rr_prune 333Integer: default interval between 334.Tn IPv6 335router renumbering prefix babysitting, in seconds. 336.It Dv IPV6CTL_V6ONLY 337.Pq ip6.v6only 338Boolean: enable/disable the prohibited use of 339.Tn IPv4 340mapped address on 341.Dv AF_INET6 342sockets. 343Defaults to on. 344.El 345.Ss Interaction between IPv4/v6 sockets 346By default, 347.Fx 348does not route IPv4 traffic to 349.Dv AF_INET6 350sockets. 351The default behavior intentionally violates RFC2553 for security reasons. 352Listen to two sockets if you want to accept both IPv4 and IPv6 traffic. 353IPv4 traffic may be routed with certain 354per-socket/per-node configuration, however, it is not recommended to do so. 355Consult 356.Xr ip6 4 357for details. 358.Pp 359The behavior of 360.Dv AF_INET6 361TCP/UDP socket is documented in RFC2553. 362Basically, it says this: 363.Bl -bullet -compact 364.It 365A specific bind on an 366.Dv AF_INET6 367socket 368.Xr ( bind 2 369with an address specified) 370should accept IPv6 traffic to that address only. 371.It 372If you perform a wildcard bind 373on an 374.Dv AF_INET6 375socket 376.Xr ( bind 2 377to IPv6 address 378.Li :: ) , 379and there is no wildcard bind 380.Dv AF_INET 381socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic 382should be routed to that 383.Dv AF_INET6 384socket. 385IPv4 traffic should be seen as if it came from an IPv6 address like 386.Li ::ffff:10.1.1.1 . 387This is called an IPv4 mapped address. 388.It 389If there are both a wildcard bind 390.Dv AF_INET 391socket and a wildcard bind 392.Dv AF_INET6 393socket on one TCP/UDP port, they should behave separately. 394IPv4 traffic should be routed to the 395.Dv AF_INET 396socket and IPv6 should be routed to the 397.Dv AF_INET6 398socket. 399.El 400.Pp 401However, RFC2553 does not define the ordering constraint between calls to 402.Xr bind 2 , 403nor how IPv4 TCP/UDP port numbers and IPv6 TCP/UDP port numbers 404relate to each other 405(should they be integrated or separated). 406Implemented behavior is very different from kernel to kernel. 407Therefore, it is unwise to rely too much upon the behavior of 408.Dv AF_INET6 409wildcard bind sockets. 410It is recommended to listen to two sockets, one for 411.Dv AF_INET 412and another for 413.Dv AF_INET6 , 414when you would like to accept both IPv4 and IPv6 traffic. 415.Pp 416It should also be noted that 417malicious parties can take advantage of the complexity presented above, 418and are able to bypass access control, 419if the target node routes IPv4 traffic to 420.Dv AF_INET6 421socket. 422Users are advised to take care handling connections 423from IPv4 mapped address to 424.Dv AF_INET6 425sockets. 426.Sh SEE ALSO 427.Xr ioctl 2 , 428.Xr socket 2 , 429.Xr sysctl 3 , 430.Xr icmp6 4 , 431.Xr intro 4 , 432.Xr ip6 4 , 433.Xr tcp 4 , 434.Xr udp 4 435.Sh STANDARDS 436.Rs 437.%A Tatsuya Jinmei 438.%A Atsushi Onoe 439.%T "An Extension of Format for IPv6 Scoped Addresses" 440.%R internet draft 441.%D June 2000 442.%N draft-ietf-ipngwg-scopedaddr-format-02.txt 443.%O work in progress material 444.Re 445.Sh HISTORY 446The 447.Nm 448protocol interfaces are defined in RFC2553 and RFC2292. 449The implementation described herein appeared in the WIDE/KAME project. 450.Sh BUGS 451The IPv6 support is subject to change as the Internet protocols develop. 452Users should not depend on details of the current implementation, 453but rather the services exported. 454.Pp 455Users are suggested to implement 456.Dq version independent 457code as much as possible, as you will need to support both 458.Xr inet 4 459and 460.Nm . 461